1. Field of the Invention
This invention is directed to alkylation of an alkyl salicylate using a long chain carbon feed (e.g., a C.sub.5 -C.sub.50 olefin or alcohol) to obtain products having a variety of uses, including use as intermediates suitable for the preparation of overbased lubricating oil additives.
2. State of the Art
Alkylation of alkyl salicylates (e.g., methyl salicylate) is known in the art. However, to effect alkylation, a liquid, gaseous or solid strong acid catalyst, such as sulfuric acid, methane sulfonic acid, molten SbCl.sub.2 --HCl, BF.sub.3, SnCl.sub.4 or an acid ion exchange resin, in combination with an alkylating feedstock and an excess of alkyl salicylate relative to the feedstock or in combination with alkyl salicylate and an excess of alkylating feedstock relative to the salicylate is typically employed in the art. Such processes are disclosed, for example, in Deutsche Patentschrifts DD 269 619 and DD 272,065, U.S. Pat. No. 5,225,588 and Japanese Patent Application No. 54/160335.
The processes disclosed in the art, however, suffer from many disadvantages. First, a combination of washing steps and/or severe stripping of the resulting crude alkylation product must be done to remove excess alkyl salicylate or excess alkylation feed, particularly long chain alkylation feed, as well as any liquid acid catalyst or dissolved gaseous acid catalyst which may have been used. However, excess alkyl salicylate or excess alkylation feed is typically employed to ensure conversion to the alkylated alkyl salicylate and, despite the resulting disadvantages of recovery, stripping of the excess alkyl salicylate or excess alkylation feed from the reaction product and recycling this excess is a necessary step from an economical point of view.
Second, the art discloses alkylation using only low carbon number alkylation feeds, for example, propylene, octene, tetradecene, styrene, isopropanol and methyl-t-butyl ether. German Patentschrift DD 269,619, for example, discloses alkylation of a salicylic acid derivative in the presence of an acidic ion exchanger as the catalyst using a linear or branched C.sub.2 -C.sub.14 olefin (optionally aryl-substituted).
The use of higher carbon number alkylation feeds is not as efficient as alkylation with lower carbon number feeds because such feeds are typically less reactive and methods of compensating for the reduced reactivity are necessary such as the use of an excess of alkyl salicylate relative to the alkylation feed.
In view of the above, methods for alkylation of alkyl salicylate using a long chain carbon feed (e.g., C.sub.15 -C.sub.50 olefin or alcohol) wherein the process does not require an excess of alkyl salicylate or an excess of alkylation feed would be desirable from both a processing point of view and an economic point of view. It would also be desirable that such methods be conducive to the efficient manufacture of alkylated alkyl salicylate.